Formation and three-dimensional architecture of Leishmania adhesion in the sand fly vector.

Attachment to a substrate to maintain position in a specific ecological niche is a common strategy across biology, especially for eukaryotic parasites. During development in the sand fly vector, the eukaryotic parasite Leishmania adheres to the stomodeal valve, as the specialised haptomonad form. Dissection of haptomonad adhesion is a critical step for understanding the complete life cycle of Leishmania. Nevertheless, haptomonad studies are limited, as this is a technically challenging life cycle form to investigate. Here, we have combined three-dimensional electron microscopy approaches, including serial block face scanning electron microscopy (SBFSEM) and serial tomography to dissect the organisation and architecture of haptomonads in the sand fly. We showed that the attachment plaque contains distinct structural elements. Using time-lapse light microscopy of in vitro haptomonad-like cells, we identified five stages of haptomonad-like cell differentiation, and showed that calcium is necessary for Leishmania adhesion to the surface in vitro. This study provides the structural and regulatory foundations of Leishmania adhesion, which are critical for a holistic understanding of the Leishmania life cycle.

Molecular detection and characterization of picobirnaviruses in piglets with diarrhea in Thailand.

Picobirnavirus (PBV) is a small, bi-segmented, double-stranded RNA virus. Taxonomically, the genus Picobirnavirus belongs to the Picobirnaviridae family. PBV infects a wide range of hosts and causes opportunistic infections, but its role in diarrheal disease remains unclear. To determine the prevalence and genetic diversity of porcine PBVs in Northern Thailand, 380 fecal samples collected from diarrheic and non-diarrheic piglets, raised in 22 pig farms, were tested for the presence of PBV. Reverse-transcription PCR (RT-PCR) was performed using primer sets specific to the RNA-dependent RNA polymerase (RdRp) gene. PBV was detected in 86 of 265 (32.5%) diarrheic piglets and in 26 of 115 (22.6%) non-diarrheic piglets. All the PBV strains detected in this study belonged to genogroup I and a high proportion of PBV-positive piglets were co-infected with group A rotavirus (RVA) and bocavirus (BoV). Phylogenetic analysis of representative genogroup I strains revealed remarkably high similarity between strains; these formed a monophyletic cluster with 97-100% sequence identity in the RdRp gene. The strains were also closely related to genogroup I PBV Chinese porcine strain. The findings indicate that PBV infection is common in piglets with and without diarrhea in Northern Thailand.